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Ng ACH, Chahine M, Scantlebury MH, Appendino JP. Channelopathies in epilepsy: an overview of clinical presentations, pathogenic mechanisms, and therapeutic insights. J Neurol 2024:10.1007/s00415-024-12352-x. [PMID: 38607431 DOI: 10.1007/s00415-024-12352-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Revised: 03/24/2024] [Accepted: 03/25/2024] [Indexed: 04/13/2024]
Abstract
Pathogenic variants in genes encoding ion channels are causal for various pediatric and adult neurological conditions. In particular, several epilepsy syndromes have been identified to be caused by specific channelopathies. These encompass a spectrum from self-limited epilepsies to developmental and epileptic encephalopathies spanning genetic and acquired causes. Several of these channelopathies have exquisite responses to specific antiseizure medications (ASMs), while others ASMs may prove ineffective or even worsen seizures. Some channelopathies demonstrate phenotypic pleiotropy and can cause other neurological conditions outside of epilepsy. This review aims to provide a comprehensive exploration of the pathophysiology of seizure generation, ion channels implicated in epilepsy, and several genetic epilepsies due to ion channel dysfunction. We outline the clinical presentation, pathogenesis, and the current state of basic science and clinical research for these channelopathies. In addition, we briefly look at potential precision therapy approaches emerging for these disorders.
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Affiliation(s)
- Andy Cheuk-Him Ng
- Clinical Neuroscience and Pediatric Neurology, Department of Pediatrics, Cumming School of Medicine, Alberta Children's Hospital, University of Calgary, 28 Oki Drive NW, Calgary, AB, T3B 6A8, Canada
- Division of Neurology, Department of Pediatrics, Faculty of Medicine and Dentistry, University of Alberta and Stollery Children's Hospital, Edmonton, AB, Canada
| | - Mohamed Chahine
- Department of Medicine, Faculty of Medicine, Université Laval, Quebec City, QC, Canada
- CERVO, Brain Research Centre, Quebec City, Canada
| | - Morris H Scantlebury
- Clinical Neuroscience and Pediatric Neurology, Department of Pediatrics, Cumming School of Medicine, Alberta Children's Hospital, University of Calgary, 28 Oki Drive NW, Calgary, AB, T3B 6A8, Canada
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Calgary, Canada
| | - Juan P Appendino
- Clinical Neuroscience and Pediatric Neurology, Department of Pediatrics, Cumming School of Medicine, Alberta Children's Hospital, University of Calgary, 28 Oki Drive NW, Calgary, AB, T3B 6A8, Canada.
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Teralı K, Türkyılmaz A, Sağer SG, Çebi AH. Prediction of molecular phenotypes for novel SCN1A variants from a Turkish genetic epilepsy syndromes cohort and report of two new patients with recessive Dravet syndrome. Clin Transl Sci 2024; 17:e13679. [PMID: 37955180 PMCID: PMC10772300 DOI: 10.1111/cts.13679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 09/23/2023] [Accepted: 09/29/2023] [Indexed: 11/14/2023] Open
Abstract
Dravet syndrome and genetic epilepsy with febrile seizures plus (GEFS+) are both epilepsy syndromes that can be attributed to deleterious mutations occurring in SCN1A, the gene encoding the pore-forming α-subunit of the NaV 1.1 voltage-gated sodium channel predominantly expressed in the central nervous system. In this research endeavor, our goal is to expand our prior cohort of Turkish patients affected by SCN1A-positive genetic epilepsy disorders. This will be accomplished by incorporating two recently discovered and infrequent index cases who possess a novel biallelic (homozygous) SCN1A missense variant, namely E158G, associated with Dravet syndrome. Furthermore, our intention is to use computational techniques to predict the molecular phenotypes of each distinct SCN1A variant that has been detected to date within our center. The correlation between genotype and phenotype in Dravet syndrome/GEFS+ is intricate and necessitates meticulous clinical investigation as well as advanced scientific exploration. Broadened mechanistic and structural insights into NaV 1.1 dysfunction offer significant promise in facilitating the development of targeted and effective therapies, which will ultimately enhance clinical outcomes in the treatment of epilepsy.
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Affiliation(s)
- Kerem Teralı
- Department of Medical Biochemistry, Faculty of MedicineCyprus International UniversityNicosiaCyprus
| | - Ayberk Türkyılmaz
- Department of Medical Genetics, Faculty of MedicineKaradeniz Technical UniversityTrabzonTurkey
| | - Safiye Güneş Sağer
- Department of Pediatric NeurologyKartal Dr. Lütfi Kırdar City HospitalİstanbulTurkey
| | - Alper Han Çebi
- Department of Medical Genetics, Faculty of MedicineKaradeniz Technical UniversityTrabzonTurkey
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Aiba I, Ning Y, Noebels JL. A hyperthermic seizure unleashes a surge of spreading depolarizations in Scn1a-deficient mice. JCI Insight 2023; 8:e170399. [PMID: 37551713 PMCID: PMC10445687 DOI: 10.1172/jci.insight.170399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 06/15/2023] [Indexed: 08/09/2023] Open
Abstract
Spreading depolarization (SD) is a massive wave of cellular depolarization that slowly migrates across the brain gray matter. Cortical SD is frequently generated following brain injury, while less is understood about its potential contribution to genetic disorders of hyperexcitability, such as SCN1A-deficient epilepsy, in which febrile seizure often contributes to disease initiation. Here we report that spontaneous SD waves are predominant EEG abnormalities in the Scn1a-deficient mouse (Scn1a+/R1407X) and undergo sustained intensification following a single hyperthermic seizure. Chronic DC-band EEG recording detected spontaneous SDs, seizures, and seizure-SD complexes in Scn1a+/R1407X mice but not WT littermates. The SD events were infrequent, while a single hyperthermia-induced seizure robustly increased SD frequency over 4-fold during the initial postictal week. This prolonged neurological aftermath could be suppressed by memantine administration. Video, electromyogram, and EEG spectral analysis revealed distinct neurobehavioral patterns; individual seizures were associated with increased motor activities, while SDs were generally associated with immobility. We also identified a stereotypic SD prodrome, detectable over a minute before the onset of the DC potential shift, characterized by increased motor activity and bilateral EEG frequency changes. Our study suggests that cortical SD is a pathological manifestation in SCN1A-deficient epileptic encephalopathy.
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Matricardi S, Cestèle S, Trivisano M, Kassabian B, Leroudier N, Vittorini R, Nosadini M, Cesaroni E, Siliquini S, Marinaccio C, Longaretti F, Podestà B, Operto FF, Luisi C, Sartori S, Boniver C, Specchio N, Vigevano F, Marini C, Mantegazza M. Gain of function SCN1A disease-causing variants: Expanding the phenotypic spectrum and functional studies guiding the choice of effective antiseizure medication. Epilepsia 2023; 64:1331-1347. [PMID: 36636894 DOI: 10.1111/epi.17509] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 01/10/2023] [Accepted: 01/10/2023] [Indexed: 01/14/2023]
Abstract
OBJECTIVE This study was undertaken to refine the spectrum of SCN1A epileptic disorders other than Dravet syndrome (DS) and genetic epilepsy with febrile seizures plus (GEFS+) and optimize antiseizure management by correlating phenotype-genotype relationship and functional consequences of SCN1A variants in a cohort of patients. METHODS Sixteen probands carrying SCN1A pathogenic variants were ascertained via a national collaborative network. We also performed a literature review including individuals with SCN1A variants causing non-DS and non-GEFS+ phenotypes and compared the features of the two cohorts. Whole cell patch clamp experiments were performed for three representative SCN1A pathogenic variants. RESULTS Nine of the 16 probands (56%) had de novo pathogenic variants causing developmental and epileptic encephalopathy (DEE) with seizure onset at a median age of 2 months and severe intellectual disability. Seven of the 16 probands (54%), five with inherited and two with de novo variants, manifested focal epilepsies with mild or no intellectual disability. Sodium channel blockers never worsened seizures, and 50% of patients experienced long periods of seizure freedom. We found 13 SCN1A missense variants; eight of them were novel and never reported. Functional studies of three representative variants showed a gain of channel function. The literature review led to the identification of 44 individuals with SCN1A variants and non-DS, non-GEFS+ phenotypes. The comparison with our cohort highlighted that DEE phenotypes are a common feature. SIGNIFICANCE The boundaries of SCN1A disorders are wide and still expanding. In our cohort, >50% of patients manifested focal epilepsies, which are thus a frequent feature of SCN1A pathogenic variants beyond DS and GEFS+. SCN1A testing should therefore be included in the diagnostic workup of pediatric, familial and nonfamilial, focal epilepsies. Alternatively, non-DS/non-GEFS+ phenotypes might be associated with gain of channel function, and sodium channel blockers could control seizures by counteracting excessive channel function. Functional analysis evaluating the consequences of pathogenic SCN1A variants is thus relevant to tailor the appropriate antiseizure medication.
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Affiliation(s)
- Sara Matricardi
- Child Neurology and Psychiatry Unit, "G. Salesi" Children's Hospital, Ospedali Riuniti Ancona, Ancona, Italy
- Department of Pediatrics, University of Chieti, Chieti, Italy
| | - Sandrine Cestèle
- Côte d'Azur University, Valbonne-Sophia Antipolis, France
- CNRS UMR7275, Institute of Molecular and Cellular Pharmacology (IPMC), Valbonne-Sophia Antipolis, France
| | - Marina Trivisano
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Full member of European Reference Network EpiCARE, Rome, Italy
| | - Benedetta Kassabian
- Neurology Unit, Department of Neuroscience, University of Padua, Padua, Italy
| | - Nathalie Leroudier
- Côte d'Azur University, Valbonne-Sophia Antipolis, France
- CNRS UMR7275, Institute of Molecular and Cellular Pharmacology (IPMC), Valbonne-Sophia Antipolis, France
| | - Roberta Vittorini
- Child and Adolescence Neuropsychiatry Service, Department of Child Pathology and Cure, Regina Margherita Children's Hospital, Turin, Italy
| | - Margherita Nosadini
- Pediatric Neurology and Neurophysiology Unit, Department of Women and Children's Health, University of Padua, Padua, Italy
| | - Elisabetta Cesaroni
- Child Neurology and Psychiatry Unit, "G. Salesi" Children's Hospital, Ospedali Riuniti Ancona, Ancona, Italy
| | - Sabrina Siliquini
- Child Neurology and Psychiatry Unit, "G. Salesi" Children's Hospital, Ospedali Riuniti Ancona, Ancona, Italy
| | - Cristina Marinaccio
- Child and Adolescence Neuropsychiatry Service, Department of Child Pathology and Cure, Regina Margherita Children's Hospital, Turin, Italy
| | - Francesca Longaretti
- Child and Adolescence Neuropsychiatry Service, S. Croce and Carle Hospital, Cuneo, Italy
| | - Barbara Podestà
- Child and Adolescence Neuropsychiatry Service, S. Croce and Carle Hospital, Cuneo, Italy
| | - Francesca Felicia Operto
- Child and Adolescent Neuropsychiatry Unit, Department of Medicine, Surgery, and Dentistry, University of Salerno, Salerno, Italy
| | - Concetta Luisi
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Full member of European Reference Network EpiCARE, Rome, Italy
- Neurology Unit, Department of Neuroscience, University of Padua, Padua, Italy
| | - Stefano Sartori
- Pediatric Neurology and Neurophysiology Unit, Department of Women and Children's Health, University of Padua, Padua, Italy
| | - Clementina Boniver
- Pediatric Neurology and Neurophysiology Unit, Department of Women and Children's Health, University of Padua, Padua, Italy
| | - Nicola Specchio
- Rare and Complex Epilepsy Unit, Department of Neuroscience, Bambino Gesù Children's Hospital, IRCCS, Full member of European Reference Network EpiCARE, Rome, Italy
| | - Federico Vigevano
- Neurology Unit, Department of Neuroscience, Bambino Gesù, IRCCS Children's Hospital, Full member of European Reference Network EpiCARE, Rome, Italy
| | - Carla Marini
- Child Neurology and Psychiatry Unit, "G. Salesi" Children's Hospital, Ospedali Riuniti Ancona, Ancona, Italy
| | - Massimo Mantegazza
- Côte d'Azur University, Valbonne-Sophia Antipolis, France
- CNRS UMR7275, Institute of Molecular and Cellular Pharmacology (IPMC), Valbonne-Sophia Antipolis, France
- Inserm, Valbonne-Sophia Antipolis, France
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Berecki G, Bryson A, Polster T, Petrou S. Biophysical characterization and modelling of SCN1A gain-of-function predicts interneuron hyperexcitability and a predisposition to network instability through homeostatic plasticity. Neurobiol Dis 2023; 179:106059. [PMID: 36868483 DOI: 10.1016/j.nbd.2023.106059] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 02/11/2023] [Accepted: 02/27/2023] [Indexed: 03/05/2023] Open
Abstract
SCN1A gain-of-function variants are associated with early onset developmental and epileptic encephalopathies (DEEs) that possess distinct clinical features compared to Dravet syndrome caused by SCN1A loss-of-function. However, it is unclear how SCN1A gain-of-function may predispose to cortical hyper-excitability and seizures. Here, we first report the clinical features of a patient carrying a de novo SCN1A variant (T162I) associated with neonatal-onset DEE, and then characterize the biophysical properties of T162I and three other SCN1A variants associated with neonatal-onset DEE (I236V) and early infantile DEE (P1345S, R1636Q). In voltage clamp experiments, three variants (T162I, P1345S and R1636Q) exhibited changes in activation and inactivation properties that enhanced window current, consistent with gain-of-function. Dynamic action potential clamp experiments utilising model neurons incorporating Nav1.1. channels supported a gain-of-function mechanism for all four variants. Here, the T162I, I236V, P1345S, and R1636Q variants exhibited higher peak firing rates relative to wild type and the T162I and R1636Q variants produced a hyperpolarized threshold and reduced neuronal rheobase. To explore the impact of these variants upon cortical excitability, we used a spiking network model containing an excitatory pyramidal cell (PC) and parvalbumin positive (PV) interneuron population. SCN1A gain-of-function was modelled by enhancing the excitability of PV interneurons and then incorporating three simple forms of homeostatic plasticity that restored pyramidal cell firing rates. We found that homeostatic plasticity mechanisms exerted differential impact upon network function, with changes to PV-to-PC and PC-to-PC synaptic strength predisposing to network instability. Overall, our findings support a role for SCN1A gain-of-function and inhibitory interneuron hyperexcitability in early onset DEE. We propose a mechanism through which homeostatic plasticity pathways can predispose to pathological excitatory activity and contribute to phenotypic variability in SCN1A disorders.
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Affiliation(s)
- Géza Berecki
- Ion Channels and Disease Group, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia.
| | - Alexander Bryson
- Ion Channels and Disease Group, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Department of Neurology, Austin Health, Heidelberg, VIC 3084, Australia
| | - Tilman Polster
- Krankenhaus Mara, Bethel Epilepsy Centre, Department of Epileptology, Medical School, Bielefeld University, Campus Bielefeld-Bethel, Bielefeld, Germany
| | - Steven Petrou
- Ion Channels and Disease Group, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Praxis Precision Medicines, Inc., Cambridge, MA 02142, USA; Department of the Florey Institute, University of Melbourne, Parkville, VIC 3050, Australia.
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Ruggiero SM, Xian J, Helbig I. The current landscape of epilepsy genetics: where are we, and where are we going? Curr Opin Neurol 2023; 36:86-94. [PMID: 36762645 PMCID: PMC10088099 DOI: 10.1097/wco.0000000000001141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
PURPOSE OF REVIEW In this review, we aim to analyse the progress in understanding the genetic basis of the epilepsies, as well as ongoing efforts to define the increasingly diverse and novel presentations, phenotypes and divergences from the expected that have continually characterized the field. RECENT FINDINGS A genetic workup is now considered to be standard of care for individuals with an unexplained epilepsy, due to mounting evidence that genetic diagnoses significantly influence treatment choices, prognostication, community support, and increasingly, access to clinical trials. As more individuals with epilepsy are tested, novel presentations of known epilepsy genes are being discovered, and more individuals with self-limited epilepsy are able to attain genetic diagnoses. In addition, new genes causative of epilepsy are being uncovered through both traditional and novel methods, including large international data-sharing collaborations and massive sequencing efforts as well as computational methods and analyses driven by the Human Phenotype Ontology (HPO). SUMMARY New approaches to gene discovery and characterization are advancing rapidly our understanding of the genetic and phenotypic architecture of the epilepsies. This review highlights relevant and groundbreaking studies published recently that have pushed forward the field of epilepsy genetics.
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Affiliation(s)
- Sarah M Ruggiero
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Julie Xian
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
| | - Ingo Helbig
- Division of Neurology, Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- The Epilepsy NeuroGenetics Initiative (ENGIN), Children’s Hospital of Philadelphia, Philadelphia, PA, 19104, USA
- Department of Biomedical and Health Informatics (DBHi), Children’s Hospital of Philadelphia, Philadelphia, PA, 19146, USA
- Department of Neurology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
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Wong JC. Gaining Awareness of Increasingly Persistent SCN1A Mutations. Epilepsy Curr 2023. [DOI: 10.1177/15357597231157484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023] Open
Abstract
[Box: see text]
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